(1) Field of the Invention
This invention relates to keyboard devices. More particularly, this invention relates to apparatus for identifying key stations and for changing key station identification.
(2) Description of the Prior Art
A conventional membrane or diaphragm keyboard includes an array of keys which may be individually actuated to close a pair of contacts of an electrical circuit associated with each of the keys. It is often considered desirable to provide for tactile feedback so that, when the keys are pressed by the finger of a person operating the keyboard, the keys "snap" and force discontinuity is transmitted to the finger of the user indicating that the key has been actuated and thus an electrical signal has been generated in the circuit associated with the key. A conventional prior art keyboard may include a flat flexible legend sheet which defines a plurality of points or areas on the sheet which the operator of a keyboard may press to actuate a snap-action element associated with the particular point or area. Typically, the points or areas on the legend sheet are indicated in some visual manner, that is, the legend sheet may have printed thereon a legend indicating the function of the key positioned beneath the legend sheet. For example, the legend sheet may include a series of numbers, letters or symbols such as those on a typewriter, or calculator or data terminal keyboard, or, the legend may indicate the particular item to be purchased at a retail outlet.
One problem with prior art keyboards having flat legend sheets is that the area or point to be actuated on the legend sheet must be visually located. Once the particular point or area on the keyboard is visually located, the person using the keyboard must position his finger or some other object directly in contact with the point or area and press downwardly to actuate a particular key. The accuracy of the data entered by means of the keyboard, accordingly, is a function of operator attentiveness. If the keys are pressed at points removed from the center of the key, the electrical circuit contacts operated by the key may be closed without providing tactile feedback or the key may provide tactile feedback without contact being made.
Copending application Ser. No. 100,861 filed Dec. 6, 1979 (assigned to the assignee hereof) disclosed keyboard structure having depressions at key locations. However, that prior application did not disclose any simple way for varying or changing key indicia.
Accordingly, it is an object of this invention to provide keyboard apparatus wherein changing or varying key indicia can be easily effected for some keys, while other keys may be permanently labeled if desired.
It is an object of the present invention to provide a keyboard wherein the keys may be located by an operator in a non-visual manner, that is, the keys may be perceived by touch in addition to being perceived visually.